1. Field of the Invention
The present invention relates to a fine sweetening agent, particularly fructose, glucose, a sugar alcohol or mixtures thereof, obtained by comminuting a corresponding crystalline material to a mean particle size of 5 to 25 .mu.m, a process for its production by counter-jet milling and classification, and its use in fondants, fillings, glazes, chocolate spreads, in the confectionery industry, specifically in chocolates, chewing-gums and dusting gum sticks, and as seed crystals in the industry preparing corresponding crystalline products. The invention also relates to products prepared using this fine sweetening agent.
2. Description of the Prior Art
With many edibles, it is desirable to replace sugar with a special sweetener. Such a sweetener may, for instance, have a lower caloric content than sucrose, be suitable for use by diabetics, and/or be dentally safe. Typical sweeteners of this kind are sugar alcohols, such as xylitol, sorbitol, lactitol, maltitol and isomalt. Fructose is an advantageous sweetener suitable for diabetics. Finely ground glucose may find use in pharmacy, for instance as a carrier.
In several applications, a sweetener must be very fine and also have a very uniform particle size. It is required of many ingested sweet products, for instance chocolate, that they sensorily have a velvety feel. This requires that the sweetener and the other solid ingredients in said products have a very small particle size. Thus for example in prepared chocolate, the proportion of grains having a size exceeding 30 .mu.m must be below 5% in order for the chocolate not to appear coarse to the tongue. This also applies to fondants employed for instance as frostings on bakery products and biscuit products (such as icings for iced doughnuts and gingerbread) and in confectionery fillings.
A sweetener having a grain size in the range 10 .mu.m-1 mm can be used for the production of chocolate when the production process is selected in accordance with the grain size. If the chocolate is produced by a process comprising mixing, rolling and conching of the ingredients, one rolling step, i.e. roll refining, is sufficient when the particle size of the sweetener is less than 200 .mu.m. In order for it to be possible to entirely omit the refining, the particle size of the sweetener must be less than about 20 .mu.m. In another chocolate process that is commonly used, a crumb-like pre-fabricate is prepared from part of the ingredients by heating them in the presence of water and evaporating the water; this pre-fabricate is called the crumb (cf. e.g. Minifie, B. W., Chocolate, Cocoa and Confectionery, second edition, AVI Publishing Company, Inc., Westport, Conn., 1982, pp. 108-113). The crumb is mixed with the other ingredients of the chocolate, refined, and conched. Also in this case the refining may be omitted, if the crumb is comminuted to a sufficient fineness prior to the addition of the other ingredients.
Fondants may be either wet fondants or dry fondants. Wet fondants comprise two phases: a solid phase formed by a fine sweetener and a syrup forming a liquid phase. Traditional wet fondants are produced either by cooling crystallization of the product into paste form or by adding the necessary liquid phase to a dry fondant. The production of a fondant and the problems associated with the storage of wet fondant have been discussed for instance in Lees, L. & Jackson, E. B., Sugar Confectionery and Chocolate Manufacture, Leonard Hill, 1973, in the section Fondants, Creams and Crystallized Confectionery (pp. 211-215). Storage problems are avoided by using dry fondants wherefrom a wet fondant may be prepared if desired, as stated previously. The conventional dry fondants comprise very fine sugar whereto a small amount of a polysaccharide doctoring/controlling the crystallization, and possibly also fat, has been added.
The production of fondants from sugar alcohols by cooling crystallization is very difficult. On the other hand, fructose and some sugar alcohols, such as xylitol, sorbitol, lactitol monohydrate, maltitol and isomalt, are difficult to grind to particle sizes below 40 .mu.m by the conventional grinding methods (based on kneading, shearing and sifting) on account of the heat sensitivity of said products.
These special sweeteners present problems also in the rolling step of chocolate production, as some of them (fructose, xylitol, sorbitol) bind water on account of their hygroscopicity, and some (for instance lactitol monohydrate and isomalt) may liberate crystal water bound to them, particularly if the refining conditions are violent. In such a case, it is difficult to closely control the content of free water in the chocolate mass, which will present production-technical problems.
For this reason, it would be important that these sweeteners could be ground to a particle size small enough to make them suitable for the production of dry fondants, and that their use would obviate the refining step of the chocolate process.
A solid dry material can be ground to a very fine particle size with a counterjet mill wherein the particles to be comminuted that are fluidized in a carrier gas, typically air, are conveyed so as to collide with one another at a high speed. Advantageously a classifier wherein the ground material is classified into fractions of varying particle sizes is provided in connection with the mill. Such apparatus and processes have been disclosed in several patent publications, for instance in Finnish Patents 62 235, 72 896, 72 897, 74 222, 77 580, 77 168 and 80 617, and they have been implemented mainly to industrial minerals and pigments that are difficult to grind. Finnish Patent Application 883405 discloses the comminution of cereal flour with a counterjet mill and classifier. Finnish Patent 85 145 discloses the comminution of a crystalline sweetener, sucralose, with a jet mill to a maximum mean particle size of 10 .mu.m, the greatest particle size being not more than twice the mean particle size. The significance of grinding has been dealt with in Eynck, V., "Dry Mixing System in Manufacture of Confectioner Coating", The Manufacturing Confectioner, October 1986, pp. 57-59.
When a counterjet mill and classifier were used for grinding fructose, glucose and sugar alcohols, very difficult problems were presented by clodding and vaulting of the material to be ground in the first tests, and the method was not suitable for industrial production. In further tests it was found that by suitable regulation of the temperature and pressure of the air employed as a carrier gas in the milling, clodding of the product could be avoided.